The presence of sulfur species in hydrocarbon fluids and aqueous streams is undesirable for various reasons. The subterranean reservoirs currently being developed have increased amounts of sulfur species within the produced hydrocarbon streams (oil and gas). Hydrogen sulfide and mercaptans are toxic gases that are heavier than air and are very corrosive to well and surface equipment.
During combustion, sulfur-rich hydrocarbon streams also produce heavy environmental pollution. When sulfur-rich streams contact metals, sulfur species lead to brittleness in carbon steels and to stress corrosion cracking in more highly alloyed materials. Moreover, hydrogen sulfide and mercaptans, in various hydrocarbon or aqueous streams pose a safety hazard and a corrosion hazard. A quick removal of these odorous and environmental malicious species would be desirable in both oilfield and refinery operations.
For the reasons mentioned, attempts have been made to wash out, or chemically convert, the sulfur species from hydrocarbon fluids and aqueous systems. Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H25), thus removing H25 and other sulfur-containing sour compounds may be understood as “sweetening”. There are several classes of sweeteners available for removing sulfur species from a hydrocarbon or aqueous stream, but many of them have serious limitations. For example, nitrogen-containing hydrogen sulfide sweeteners, such as hydrotriazine-based additives, have been in the industry for a long while now. However, the amines released while scavenging the sulfur species pose an overhead corrosion threat in various downstream processes, including distillation columns. Formaldehyde is a nitrogen-free sweetener, but it is also a potential carcinogen. Glyoxal is another nitrogen-free hydrogen sulfide sweetener, but its application is often limited due to its corrosivity and low boiling point. Metal oxides have also been proposed, but such applications are narrowed by the handling challenges and solid residual formation concerns to downstream refining catalysts and processes. Acrolein is a clean and extremely potent hydrogen sulfide/mercaptan sweetener, but it requires special handling due to toxicity concerns.
Thus, it would be desirable if a non-nitrogen sweetener could be discovered that has improved efficiency and capacity for increased sulfur-compound removal, and is less corrosive, easy to handle, as well as having a lesser degree of flash point concern.